Plug for drawing tubes



Dec. 6, 1938. G H, BRADLEY ET A 2,139,539

PLUG FOR DRAWING TUBES Filed June 1, 1937 FIG. I.

- INVENTOR GUY H. BRA DLEY.

l GEORGE E. CLIFFORD.

ATTORNE Patented Dec. 6, 1938 PLUG FOR DRAWING TUBES Guy H. Bradley, Royal Oak, and George E. Cliffprd, Detroit, Mich., assignors to Wolverine Tube Company, Detroit, Mich., a corporation of Michigan Application June 1, 1937, Serial No. 145,914

21 Claims. (Cl. 205-7) The present invention relates to apparatus for drawing seamless tubing and more particularly to that type of drawing apparatus which utilizes a pin and plug coacting with a die to produce the tube in ,the drawing operation. The specific drawing apparatus employed includes a die having a tapered or conical reducing portion which merges into the final drawing portion of the die, and a combined draw pin and plug, the latter having a surface designed to mate accurately with the reducing portion of the die.

The invention further contemplates the provision of lubricating means associated with the pin and plug, the lubricating means being flexible to permit the same to accommodate itself to inaccuracies in the material being drawn. The invention also includes a resilient compressible element which frictionally engages the tube during its forward movement, tending to advance the plug into mating relation with the reducing portion of the die.

A further feature of this invention consists in the provision of a combined draw pin and plug having a tail piece sufiiciently flexible to insure proper engagement of the plug in the die, irrespective of irregularities in the contour of the tubing being drawn.

In addition to the foregoing, this invention contemplates a tail piece for the plug comprising a relatively closely wound coil spring of substantial length, either fixed to or removable from the tail piece and adapted to contain a suflicient quantity of lubricant toeifectively lubricate relatively long lengths of tubing during the .drawing operation. In cases where the spring is removable, the quantity of lubricant may be varied to suit the length of the tubing being drawn by merely interchanging the spring with springs of varying diameter and length.

In the drawing of seamless tubes it has been customary, in one type of apparatus, to reduce the diameter of the tube in the die immediately prior to the passage thereof through the throat portion of the die. This reduction is efiected by drawing the tube through a flared passage in the die around a plug positioned in the passage. In some instances, the plug has a rounded or spherical surface, between which and the surface of the flared passage the material is drawn to contract the tube just prior to the ultimate drawing operation, that is, the final reduction in the rectilinear throat portion of the die in which the draw pin is positioned. When the surface of the plug is rounded, however, there is produced a line contact between the tube material and the die,

resulting in uneven wear of the die in a single transverse plane therethrough. In the present invention, the mating surfaces of the tapered plug and flared portion of the die insure a relatively large contact area during contraction of the tube and a corresponding distribution of bearing pressures. In this manner, the wear on the die is distributed over a greater area than is possible when the plug is rounded or has an abrupt ironing edge.

The foregoing objects, as well as other features of the invention, will be made more apparent as this description proceeds, especially when considered in connection with the accompanying drawing, wherein:-

Figure 1 is an elevation partly in section of the assembled die and draw pin, showing the 'plug, the lubricating rings, and advancing device;

Figure 2 is a sectional view of the detachable advancing means and lubricating ring h'older;

Figure} is an enlarged fragmentary elevation partly in section of the die and combined draw pin. and plug;

Figure 4 is a sectional view of a modified form of advancing device and ring holder;

Figure 5 is a side elevational view, partly in section, of a modified form of draw pin;

Figure 6 is a longitudinal sectional view through the draw pin shown in Figure 5;

Figure 7 is a side elevational view of still another embodiment of the invention; and

Figure 8 is a longitudinal sectional view through'the draw pin disclosed in Figure 7.

This application is a continuation in part of our copending application Serial No. 81,762, filed May 25, 1936. Referring now more in detail to the embodiment of the invention illustrated in Figures 1 to 3, inclusive, it will be noted that in Figure 1 the combined pin and plug 9 is shown as centered in and coacting with a die "I. Detachably securedto plug 9 is a tail piece II, in' the present instance a wire member l2, to the forward end of which is securedin any suitable manner a threaded sleeve l3 adapted to be threaded into a tapped recess It in the rear face of the plug. Mounted on wire l2 are a plurality of felt rings l5 held thereon inspaced relation by a number of interposed washers l6 and by a tapered guide or spreader ll secured to the wire rearwardly of the felt rings. The wire I2 is bent to form a loop indicated at I, the end of the looped portion being likewise secured to guide piece II. The looped portion is preferably D -n wire, or similar material, which is resilient and springy, so that the loop 18 is compressible.

Referring to Figure 3, the draw pin comprises a rectilinear drawing portion [9 (the draw pin proper), an enlarged tapered portion 2|, which for cylindrical tubes is conical, and a rectilinear rear portion 22 having rounded corners 23. At the junction of the drawing portion and the plug a rounded shoulder 24 is provided to permit the metal to spread slightly previous to being drawn through the drawing portion of the die. Forwardly of the draw pin there is a reduced portion 20 provided primarily to avoid fringing or peeling of plating material with which the draw pin surface is coated. If, in the plating of the pin, the forward edge of the drawing portion l9 were the terminal of the cathode, there would be a tendency for the plating to build up on the surface of the drawing portion adjacent said edge, increasing its diameter at this point. The provision of the reduced forward extension obviates this difficulty, inasmuch as any building up of the plating occurs at the end of the extension. Since this portion plays no' part in the actual drawing of the material, irregularities in its diameter are immaterial.

The die is apertured rectilinearly at 25, the surface of this portion constituting the finishing face or throat of the die. The forward comer of this portion is as shown at 26. The die throat merges into a flared mouth portion 21 designed to contract the tube material prior to its passage be tween the draw pin and die.

The draw pin and plug are designed to mate with the throat and mouth of the die, respectively, thus providing a large contact area between the tube material and the surfaces of the mouth of the die and the plug. As shown in the drawing, the angularity of the plug and die mouth differ with respect to each other in that the included angle A of the die mouth is slightly less than the included angle B of the plug. This variation in angularity of the plug and die mouth is advantageous in that it compensates-for any thickening of the tube walls resulting from the contracting operation. However, it is to be understood that in cases where there is no tendency for the tube walls to thicken during the drawing. operation, the plug angle is maintained the same as the included angle of the die. Under normal conditions of drawing, the tube becomes thicker adjacentthe throat of the die and, as that action takes place, the space between the die mouth and the plug gradually decreases toward the throat to provide for extended surface contact between the exterior of the tube and the die mouth and between the interior of the tube and the plug. Seating the plug in the mouth in this manner insures a more uniform distribution of bearing pressure and longer life of the die. There is also a definite relation between the length of the draw pin and the throat or land of the die. The draw pin extends sufflciently back of the throat to permit spreading of the metal previous to drawing and forwardly a suillcient distance beyond the throat to insure proper drawing. Its

projection beyond the throat bears a definite relation to its length, however, so that there is eliminated the danger of too great an overhang and whipping", as might occur when too short a pin is employed.

Attached to plug 9 is the tail piece ll previously referred to herein. This piece is designed to perform the several functions of advancing the plug, guiding tube material thereover, and

lubricating the tube prior to the drawing operation. The looped portion [8 is compressible and adapted to frictionally engage the tube and, because it tends to move with thematerial, to urge the plug towards the throat of the die. It will be apparent, therefore, that the plug maintains its mating relation with the mouth of the die and that anchoring means therefor are unnecessary. The tapered guide I! spreads the tube, if there is any unevenness therein, and the rearwardmost ring 15 removes saw chips or other foreign material likely to become wedged between the die and plug, and damage the inner surface of the tube during the drawing operation. It will be seen that the guide is provided with a straight portion 28 adjacent the rearwardmost lubricating ring, thus providing a pocket or recess in which the foreign material will lodge so as to be prevented from being carried over the lubricating rings. By straightening out the uneven inner surface of the tube and removing foreign matter therefrom previous to lubracting it, damage to rings I5 is minimized. The interposition of spaced washers l6 permits each of the rings to flex more freely, further lessening the possibility of damage to the rings from any unevenness in the tube. Because the rings are flexible and resilient, they adjust themselves to such inaccur acies as might be present in the tube material but, nevertheless, perform their intended functions.

In Figure 4 is shown a modified form of advancing device in which the supporting element for the lubricating rings and washers consists of a threaded rigid member 30, for instance, a screw of suitable length. In this construction, the washers may be replaced by nuts. Soldered or otherwise secured to one end of member 30 is a coiled wire 3|, the diameter of the coil being such that the wire engages the interior of the tube and advances the plug in much the same manner as the looped portion I8 in Figure 2.

The embodiment of the invention illustrated in Figures 5 and 6 difiers from the one previously described in the construction of the tail piece 32. The tail piece 32 is shown in Figure 6 as comprising a single length of spring wire 33 having a forwardly projecting axially extending portion 34 secured at its forward end to a fastener element 35 having an enlarged annular portion 36 and having a threaded reduced shank 31 attached to the rear end of the plug 3 in the same manner as the tail piece H in the first described form of the invention is secured to the plug 9. The rear end of the axially extending portion 34 is fashioned to form an axially elongated loop 38, and the free end of the loop is coiled around the straight portion 34 of the wire to form an axially extending spring 39. In the present instance, the free end of the loop is coiled in such a manner as to locate the convolutions of the spring in contacting relation, and the convolutions at the forward end of the spring are sleeved over the enlarged portion 36 of the fastener. In actual practice, it is desired to prevent axial displacement of the spring 39 relative to the fastener element 35 and this result is accomplished herein by brazing or otherwise securing the convolutions at the forward end of the spring to the enlarged head at the rear end of the fastener element.

M in the first described form of the invention,

the elongated loop 38 is compressible and is normallv of suflicient width to frictionally engage the inner side wall of the tube to be drawn. Due

to thisf rictional engagement, the tail piece tends to move with the tube and in so doing urges the plug 9 towards the die' III. The entire tail piece forming the subject matter of this embodiment of the invention difiers from the one previously described in that it is highly flexible and, as a consequence, will readily adjust itself to curvatures or irregularities in the tubing without a1- fecting the cooperative relationship between the plug 9' and the die I. In other words, the plug 9' is maintained in proper seating relationship in the die to effectively plug the tubing, irrespective of lateral displacement of the tail piece relative to the plug. It is important that the tubing be properly plugged during the drawing oper-' ation not only from the standpoint of maintaining maximum efiiciency in drawing the tube, but also to prevent escape of lubricant past the plug, since this lubricant will burn on the tubing wall during the subsequent annealing operation.

The spring 39, in addition to providing the desired flexibility between the plug and tail piece, further insures efiicient lubrication of the tubing during the drawing operation. Inthe present instance, the spring 39 is packed with a lubricant which escapes from the interior of the spring between .the adjacent convolutions on the inner wall of the tubing as the latter is subjected to the drawing operation. Thus, it will be seen that the spring 39 forms, in effect, a lubricant, retainer and the length, as well as the diameter of this spring, may be varied to accommodate the volume of lubricant required to effectively lubricate the length of tubing to be drawn.

The tail piece 40 shown in Figures '7 and 8 is similar in principle of operation to the one previously described, but differs structurally therefrom in that the spring 4| is separate and removable from the section 42. As a result, the spring 4| may not only be readily interchanged for springs of different dimension to accommodate varying quantities of lubricant, but any chips or other foreign matter accumulating in the spring may be readily removed. a

In detail, the section 42 of the tailpiece 44 comprises a strip of spring wire having an axially ex tending forwardly projecting portion 43 integrally connected to the rear end of a fastener element 44 having an enlargement 45 at the rear end and having a forwardly projecting threaded portion 46 attachable to the plug 9" in accordance with any one of the foregoing embodiments of this invention. The rear end of the axially extending portion 43 is fashioned to form an axially elongated loop 41, and the free end 48 of this loop is extended into the spring 4| through the forward end of the latter to be held under tension by the spring.

Owing to the fact that the free end 48 of the loop 41 is not attached, it follows that this loop is highly compressible and that the spring 4| may be sleeved over the loop to the portion thereof shown in Figure 8, notwithstanding the fact that the diameter of the spring is substantially less than the width of the loop. The maximum width of the loop 4! is such as to frictionally engage the inner wall of the tubing and to maintain the plug in proper cooperative relation with the die l0" during the drawing operation. It will also be noted that the tail piece shown in Figures 7 and 8 is highly flexible to compensate for curvatures or irregularities in the tubing without disturbing on the enlargement 45 and is hld in assembled.

relation with the enlargementby means of the loop 41, due to the tendency of the opposite side portions of the loop to spring apart. It will, of

course, be understood from Figure 7 that the forward end of the spring 4| abuts the rear side of the plug 9' and, in order to avoid any tendency for the spring to slip over the plug during operation, the adjacent convolutions of the spring at the forward end thereof are brazed or otherwise secured together to form, in effect, a rigid sleeve. In the present instance, the adjacent convolutions at the rear end of the spring are also secured together so that the spring is interchangeable end for end.

As in the embodiment of the invention illustrated in Figures and 6, the spring 4| forms a retainer for lubricant, and this lubricant is permitted to escape between adjacent convolutions of the spring from the interior of the spring to the side walls of the tubing. The amount of lubricant necessary depends to a great extent upon the length of the tubing to be drawn and the spring 4| is interchangeable for springs of different length and diameter to accommodate more or less the lubricant.

The invention has been described more particularly as applied to cylindrical tubes, but tubes of other geometrical sections may be drawn with the apparatus, it being only necessary to provide the proper cross sectional shapes for the several parts. The tapered portions of the die and plug have been shown as straight, but if desired, a curved surface may be substituted therefor provided the cooperating surfaces are mated to in-' sure a large contact area and uniform distribution of bearing surfaces. Other changesin the component parts of the apparatus may be made without departing from the contemplated objects of the invention as claimed.

What we claim as our invention is:

1. An apparatus for drawing tubes comprising a die having a tapered reducing portion and a throat,adjacent the smaller end of the reducing portion, a draw pin including a plug thereon,

said plug coacting with said reducing portion, and a resilient element connected at one end to said plug and having its other end formed to frictionally engage a tube being drawn tending to advance the plug with the tube toward said 7 4. An apparatus for drawing tubes comprisingv a die having a tapered reducing portion and a throat adjacent the smaller end of the reducing portion, a draw pin including a plug thereon, said plug coacting with said reducing portion, a member connected at one end to said plug having a compressible rearend portion adapted to frictionally engage a tube being drawn, and spaced lubricating members supported by said member in advance of the compressible portion.

5. An apparatus for drawing tubes comprising a die having a tapered reducing portion and a throat adjacent the smaller end of the reducing portion, a draw pin including a plug thereon, said plug coacting withsaid reducing portion, tube straightening means attached to said plug rearwardly thereof, and a lubricant retaining pad secured to the plug in advance of the straightening means and engageable with the inner surface of a tube being drawn.

6. An apparatus for drawing tubes comprising a die having a tapered reducing portion and a throat adjacent the smaller end of the reducing portion, a draw pin including a plug thereon, said plug coacting with said reducing portion, a tapered tube guide attached to said plug rearwardly thereof, and a compressible element carried by the plug rearwardly oi the guide and adapted to frictionally engagea tube being drawn in a manner to apply a force on the tube tending to advance the plug toward said throat.

'7. An apparatus for drawing tubes comprising a die having a tapered reducinglportion and a throat adjacent the smaller end of the reducing portion, a draw pin including a plug thereon, said plug coacting with said reducing portion, a supporting element connected at one end to said plug, a tapered tube guide connected to said element, and resilient lubricating means positioned on said element between said guide and said plug.

8. An apparatus for drawing tubes comprising a die having a tapered reducing portion and a throat adjacent the smaller end of the reducing portion, a draw pin including a plug thereon, said plug coacting with said reducing portion, a supporting element connected at one end to said plug and having its other end formed to frictionally engage a tube being drawn, a tapered tube guide on said element, and resilient lubricating means positioned on said element between said guide and said plug.

9. An apparatus for drawing tubes comprising a die having a tapered reducing portion and a throat adjacent the smaller end of the reducing portion, a draw pin including-a plug thereon, said plug coacting with the reducing portion, and a compressible lubricant retaining member connected to the rear end of the plug to form a unit with the latter and engageable with the inner surface of a tube being drawn to lubricate said surface.

10. An apparatus for drawing tubes comprising a die having a tapered reducing portion and a throat adjacent the smaller end of the reducing portion, a draw pin including a plug thereon, said plug coacting with the reducing portion, and compressible lubricant retaining pads connected to the rear end of the plug in spaced relation axially of the latter and engageable with the inner surface of a tube being drawn to lubricate said surface.

11. An apparatus for drawing tubes comprising a die having a tapered reducing portion through which a length of tubing is to be drawn, a plug over which the tubing is drawn and supported in cooperative relation with the reducing portion of the die, and means for maintaining the plug in cooperative relation with the die including a flexible member extending rearwardly from the plug and having a compressible portion frictionally engageable with the inner surface of the tube being drawn.

12. An apparatus for drawing tubes comprising a die having a tapered reducing portion through which a length of tubing is to be drawn, a plug over which the tubing is drawn and supported in cooperative relation with the reducing portion of the die, means for maintaining the plug in cooperative relation with the die including a flexible member extending rearwardly from the plug and having a compressible portion frictionally engageable with the inner surface of the tube being drawn, and means mounted on the flexible member between the compressible portion thereof and plug for distributing lubricant on the tubing.

13. An apparatus for drawing tubes comprising a die having a tapered reducing portion through which a length of tubing is drawn, a plug over which the tubing is drawn supported in cooperative relation with the reduced portion of the die, a flexible member extending rearwardly from the plug and having a portion frictionally engageable with the inner surface of the tubing to maintain the plug in cooperative relation with the reduced portion of the die, and lubricant retaining means removably mounted on said member between the portion aforesaid thereof and said plug.

14. An apparatus for drawing tubes comprising a die having a tapered reducing portion through which a length of tubing is drawn, a plug over which the tubing is drawn supported in cooperative relation with the die, a member extending rearwardly from the plug and having a portion frictionally engageable with the inner surface of the tubing to maintain the plug in cooperative relation with the die, and a coil spring on said member between the portion aforesaid thereof and the plug and'adapted to contain a supply of lubricant.

15. An apparatus for drawing'tubes comprising a die having a tapered reducing portion through which a length of tubing is drawn, a plug over which the tubing is drawn supported in cooperative relation with the reduced portion of the die, a flexible member extending rearwardly from the plug and having a portion adjacent the rear end thereof frictionally engageable with the inner surface of the tubing to maintain the plug in operative relation with the die during the drawing operation, and a coil spring adapted to retain a lubricant removably supported on the flexible member between the plug and the portion aforesaid of said member.

16. An apparatus for drawing tubes comprising a die having a tapered reducing portion through which a length of tubing is drawn, a plug over which the tube is drawn supported in cooperative relation with the reducing portion of the die, a flexible member extending rearwardly from the plug and having a compressible portion at the rear end frictionally engageable with the inner surface of the tubing to maintain the plug in cooperative relation to the die during the drawing operation, and lubricant retaining means comprising an elongated coil spring movable over the compressible portion to a position on the member adjacent the plug and held in assembled relation with the member by the tension of the compressible portion.

1'7. An apparatus for drawing tubes comprising a die having a tapered reducing portion'through which a length of tubing is adapted to be drawn, a plug over which the tubing is adapted to be drawn supported in cooperative relation to the die, a lenght of spring wire extending rearwardly from the plug and looped back toward the plug to form a compressible portion frictionally engageable with the inner surface of the tubing to maintain the plug in cooperative relation with the die during the drawing operation, the free end of said loop being coiled around the portion of the spring wire adjacent the plug to form a spring adapted to contain a supply of lubricant.

extremity thereof extending into the rear end of tionship and having a width suflicientfto fric-.

tionally engage the inner side walls of the tube being drawn to maintain the plug in cooperative relation with the die during the drawing operation.

19. An apparatus for drawing tubing comprising a die having a tapered reducing portion through which a length of tubing is adapted to be drawn, a plug over which the tubing is adapted to be drawn supported in cooperativerelation with the reducing portion of the die, a length of flexible spring wire extending rearwardly from the plug and looped back toward the plug to form a compressible portion frictionally engageable with the inner surface of the tubing to be drawn to maintain the plug in cooperative relation with the die, and a lubricant retaining coil spring of less diameter than the tubing insertable over the looped portion of the spring wire to a position adjacent the rear side of the plug.

20. An apparatus for drawing tubes comprising a die having a tapered 'reducing portion through which a length of tubing is adapted to be drawn; a plug over which the tubing is adapted to be drawn supported in cooperative relation to the reducing portion of the die, a flexible member extending rearwardly from the plug and having a compressible portion adjacent the rear end frictionally engageable with the inner surface of the tubing to hold the plugin cooperative relation to the die during the drawing operation, said flexible member also having an enlargement adjacent the rear side of the plug, and a lubricant retaining spring supported on the flexible member adjacent the rear 'side of the plug and having the convolutions at the end thereof integrally united and sleeved over said enlargement.

21. In apparatus for drawing tubes comprising a die having a tapered reducing portion through which a length of tubing is adapted to be drawn, a plug over which the tube is adapted to be drawn supported in cooperative relation with the die, a flexible member having'a fastener element at the forward end detachably secured to the rear end of the plug and provided with an enlargement, said flexible member extending rearwardly from the fastener element and having a compressible portion adjacent the rear end frictionally engageable with the inner surface of the tubing to maintain the plug in cooperative relation to the die, and a lubricant retaining spring positioned upon saidmember adjacent the rear side of the plug and having the convolutions at the forward end encirclingthe enlargement on said fastener element. r

. GUY H. BRADLEY.

GEORGE E. CLIFFORD. 

